This invention relates to dynamic or centrifugal balancing machines, and in particular, to automatic detection and positioning of the unbalance location of a rotor piece to a desired angular position.
In order to remove residual unbalance of worked rotor pieces, there have been used dynamic or centrifugal balancing machines where, during rotating the rotor piece, amount and angular location of the unbalance are detected. The detected unbalance is removed by a machine such as a grinding machine, a drilling machine and others.
In known dynamic balancing machines, a test rotor piece is rotatably supported on flexible bearings at opposite axial ends and is rotated. Pick-up units are coupled with the bearings to pick up once-per-revolution vibratory motion of the bearings of forces on the bearings due to unbalance in the test rotor. Vibration velocity pick-up units are usually used. Amounts of unbalance at axial opposite end planes of the rotor are obtained from amplitudes of signals picked up by respective pick-up units. In order to obtain unbalance measurements that apply to each balance plane separately, picked-up signals by both pick-up units are processed in plane separation circuits.
There have been known two typical ways in the prior art for detecting the angular location of unbalance of the rotor, one of which is, so called, the stroboscopic type, the other being the photocell type. Those two types will be described thereinafter referring to the accompanying drawings.
The former is known to be simple and the machine is relatively inexpensive. However, the operator must mark numbers on the test rotor piece and memorize the angle after measurement. Accordingly, the subsequent correction of the unbalance is subject to errors, meaning that the efficiency of the balancing work depends largely on the skill of the operator. Another problem is strain caused by stroboscopic flashing to the operator's eyes.
The latter is more advanced as the angular position can be presented in the form of an electrical signal for indication on a meter. However, the operator must still paint the reference mark on the test rotor piece. Furthermore, the operator must estimate the correct position corresponding to the angle on the meter as indicated assuming the reference mark to be 0.degree.. This results in a phase error thereby causing an insufficient correction.